CPV tests with rare kaon decays

Abstract

The K_S \to pi+/- e+ e- decay mode has been investigated using the data collected in 2002 by the NA48/1 collaboration. With about 23k signal events and 59k K_L \to pi+ pi- pi0_D normalization decays, the K_S \to pi+ pi- e+ e- branching ratio was determined. This result is also used to set an upper limit on the presence of E1 direct emission in the decay amplitude. The CP-violating asymmetry has been also measured. We report on measurements of the rare decays K +/- \to pi+/- e+ e- and K+/- \to pi+/- mu+ mu- . The full NA48/2 data set was analyzed, leading to more than 7200 reconstructed events in the electronic and more than 3000 events in the muonic channel, the latter exceeding the total existing statistics by a factor of four. For both channels the selected events are almost background-free. From these events, we have determined the branching fraction and form factors of K+/- \to pi+/- e+ e- using different theoretical models. Our results improve the existing world averages significantly. In addition, we measured the CP violating asymmetry between K+ and K- in this channel to be less than a few percent.

arXiv comment4 pages, 1 figure, To appear in the proceedings of IX International Conference on Hyperons, Charm and Beauty Hadrons (BEACH2010), Perugia, Italy, 21-26 June 2010

References in corpus (12)

• Big Bang Nucleosynthesis (in "The Review of Particle Properties" 2004)
• A precision measurement of direct CP violation in the decay of neutral kaons into two pions
• The Decays $K\to \pi {\ell }^{+}{\ell }^{-}$ beyond Leading Order in the Chiral Expansion
• Search for direct CP violating charge asymmetries in $K^{\pm }\to {\pi }^{\pm }{\pi }^{+}{\pi }^{-}$ and $K^{\pm }\to {\pi }^{\pm }{\pi }^0{\pi }^0$ decays
• Rare Kaon Decays Revisited
• Precise measurement of the K+- --> pi+-e+e- decay
• Rare Kaon Decays in the $1/N_c$-Expansion
• A new measurement of the properties of the rare decay K -> pi+ e+ e-
• Observation of the Decay K- -> pi- mu+ mu- and Measurements of the Branching Ratios for K+/- -> pi+/- mu+ mu-
• A New Measurement of the Rare Decay $K^{+}\to {\pi }^{+}{\mu }^{+}{\mu }^{-}$
• Forward-backward Asymmetry in $K^{+}\to {\pi }^{+}{\ell }^{+}{\ell }^{-}$
• Long-distance contribution to the forward-backward asymmetry in decays K+ --> pi+ l+ l-